1. Field of the Invention
The present invention relates to a method of sensor network localization and, more particularly, to a method of sensor network localization through reconstruction of a radiation pattern with a characteristic value of an antenna depending on orientation thereof.
2. Description of the Related Art
A wireless sensor network is composed of interconnected sensor nodes which are small computing devices for wireless communication. The wireless sensor network has been increasingly applied to military applications, traffic automation, and location based services as well as traditional technical fields such as environmental information monitoring or data collection. The wireless sensor network is suitable for efficiently collecting distributed data from remote nodes and providing customized services.
For a location based service, user location information is important in a sensor network. Accordingly, a number of algorithms have been proposed to estimate the location information. Such localization algorithms can be divided into an active localization scheme and a passive localization scheme depending on how signals related to localization are produced.
The active localization scheme refers to a technique in which devices involved in a system, a network infrastructure or a network can produce signals required for localization and estimate the location with the signals. Most reliable systems, such as radar or sonar systems, which estimate location using wave reflection, and global positioning systems (GPS), which use signals transmitted from satellites to the earth, are based on the active localization technique. However, drawbacks of the active localization technique include relatively expensive components or devices and high power consumption compared with the passive localization technique.
On the other hand, the passive localization scheme is a technique of estimating locations without information produced for the purpose of localization. The passive localization technique generally uses time difference of arrival (TDOA), angle of arrival (AOA) or received signal strength (RSS) of a sound or an electric wave of a localization target. The passive localization technique requires less cost but provides a lower quality than the active localization technique. For a wireless sensor network, however, since a number of sensor nodes are distributed in a wide area, network expansion should be considered to provide a localization system. Moreover, since the localization system requires efficient operation in a limited environment, the active localization technique is not appropriate for the sensor network environment in terms of efficiency. Hence, research into localization with the passive localization technique has been actively conducted in the fields related to the wireless sensor network. Above all, research into systems using the RSS scheme are most actively carried out, since the systems require no additional equipment and infrastructure and thus are suitable for a sensor network environment with limited resources.
For the RSS scheme, however, it is not easy to obtain distance information from a signal due to reflection, attenuation or diffusion of the signal. Furthermore, for the RSS scheme, RSS fluctuation occurs with time due to signal interference, thereby causing localization errors.